Work out the length of the perimeter.

Try this option:
According to property such triangle
1. area=0.5*a*b, where a and b - the sides of angle 90°.
Using this equation: 180=0.5*40*b, ⇒ b=9.
2. c²=a²+b², ⇒c=√(9²+40²)=41 - the third side of the triangle;
3. Perimeter=a+b+c=9+40+41=90 cm.

90 cm.

A: 18/15b : 7 - -8 = 15 , 12 - -6 = 18 the y variable always goes over the x variables, c : same thing a